我使用FFmpeg解码H.264视频，用于以下程序：
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/time.h>
#include <time.h>
#include <libavcodec/avcodec.h>
#include <libavutil/mathematics.h>
#include <SDL/SDL.h>
void sigint_handler(int signal) {
printf("\n");
exit(0);
}
const char *window_title;
SDL_Surface *screen;
SDL_Overlay *yuv_overlay;
#define INBUF_SIZE 80000
/*
* Video decoding example
*/
static long get_time_diff(struct timeval time_now) {
struct timeval time_now2;
gettimeofday(&time_now2,0);
return time_now2.tv_sec*1.e6 - time_now.tv_sec*1.e6 + time_now2.tv_usec - time_now.tv_usec;
}
int video_open(AVCodecContext *avctx, const char *filename){
int flags = SDL_HWSURFACE|SDL_ASYNCBLIT|SDL_HWACCEL;
int w,h;
flags |= SDL_RESIZABLE;
if (avctx->width){
w = avctx->width;
h = avctx->height;
} else {
w = 640;
h = 480;
}
if(SDL_Init(SDL_INIT_VIDEO) < 0) {
fprintf(stderr, "SDL_INIT_VIDEO failed!\n");
exit(1);
}
screen = SDL_SetVideoMode(w, h, 0, flags);
if (!screen) {
fprintf(stderr, "SDL: could not set video mode - exiting\n");
return -1;
}
if (!window_title)
window_title = filename;
SDL_WM_SetCaption(window_title, window_title);
yuv_overlay = SDL_CreateYUVOverlay(w, h, SDL_YV12_OVERLAY, screen);
if (yuv_overlay->hw_overlay) {
fprintf(stderr, "Using hardware overlay!\n");
}
return 0;
}
int main(int argc, char **argv) {
AVCodec *codec;
AVCodecContext *c= NULL;
AVCodecParserContext *parser = NULL;
int frame, got_picture, len2, len;
const char *filename;
FILE *f;
AVFrame *picture;
char *arghwtf = malloc(INBUF_SIZE);
char *luma = NULL;
char *chroma = NULL;
int i=0;
uint64_t in_len;
int pts, dts;
struct timeval t;
float inv_fps = 1e6/23.98;
AVPacket avpkt;
SDL_Rect rect;
/* register all the codecs */
avcodec_register_all();
filename = argv[1];
av_init_packet(&avpkt);
printf("Decoding file %s...\n", filename);
/* find the H.264 video decoder */
codec = avcodec_find_decoder(CODEC_ID_H264);
if (!codec) {
fprintf(stderr, "codec not found\n");
exit(1);
}
c = avcodec_alloc_context3(codec);
picture = avcodec_alloc_frame();
c->skip_loop_filter = 48; // skiploopfilter=all
if (avcodec_open(c, codec) < 0) {
fprintf(stderr, "could not open codec\n");
exit(1);
}
/* the codec gives us the frame size, in samples */
parser = av_parser_init(c->codec_id);
parser->flags |= PARSER_FLAG_ONCE;
f = fopen(filename, "rb");
if (!f) {
fprintf(stderr, "could not open %s\n", filename);
exit(1);
}
frame = 0;
gettimeofday(&t, 0);
if(fread(arghwtf, 1, INBUF_SIZE, f) == 0) {
exit(1);
}
in_len = 80000;
while (in_len > 0 && !feof(f)) {
len = av_parser_parse2(parser, c, &avpkt.data, &avpkt.size, arghwtf, in_len,
pts, dts, AV_NOPTS_VALUE);
len2 = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
if (len2 < 0) {
fprintf(stderr, "Error while decoding frame %d\n", frame);
exit(1);
}
if (got_picture) {
if(!screen) {
video_open(c, filename);
rect.x = 0;
rect.y = 0;
rect.w = c->width;
rect.h = c->height;
inv_fps = av_q2d(c->time_base);
fprintf(stderr, "w:%i h:%i\n", rect.w, rect.h);
luma = malloc(c->width*c->height);
chroma = malloc(c->width*c->height/4);
SDL_DisplayYUVOverlay(yuv_overlay, &rect);
signal(SIGINT, sigint_handler);
}
fprintf(stderr, "\rDisplaying %c:frame %3d (%02d:%02d)...", av_get_pict_type_char(picture->pict_type), frame, frame/1440, (frame/24)%60);
fflush(stderr);
SDL_LockYUVOverlay(yuv_overlay);
for(i=0;i<c->height;i++) {
memcpy(luma + i * c->width, picture->data[0] + i * picture->linesize[0], c->width);
}
memcpy(yuv_overlay->pixels[0], luma, c->width * c->height);
for(i=0;i<c->height/2;i++) {
memcpy(chroma + i * c->width/2, picture->data[2] + i * picture->linesize[2], c->width/2);
}
memcpy(yuv_overlay->pixels[1], chroma, c->width * c->height / 4);
for(i=0;i<c->height/2;i++) {
memcpy(chroma + i * c->width/2, picture->data[1] + i * picture->linesize[1], c->width/2);
}
memcpy(yuv_overlay->pixels[2], chroma, c->width * c->height / 4);
SDL_UnlockYUVOverlay(yuv_overlay);
SDL_DisplayYUVOverlay(yuv_overlay, &rect);
while(get_time_diff(t) < inv_fps) {
sleep(1000);
}
frame++;
gettimeofday(&t, 0);
}
memcpy(arghwtf, arghwtf + len, 80000-len);
fread(arghwtf + 80000 - len, 1, len, f);
}
/* some codecs, such as MPEG, transmit the I and P frame with a
latency of one frame. You must do the following to have a
chance to get the last frame of the video */
avpkt.data = NULL;
avpkt.size = 0;
len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
if (got_picture) {
printf("saving last frame %3d\n", frame);
fflush(stdout);
/* Display last frame here, same code as in the decoding loop above. */
frame++;
}
fclose(f);
avcodec_close(c);
av_free(c);
av_free(picture);
printf("\n");
}
它给出错误：
||=== H264_decoding, Debug ===|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp||In function ‘int main(int, char**)’:|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|107|error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|136|warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /home/yoohoo/ffmpeg_build/include/libavcodec/avcodec.h:3629) [-Wdeprecated-declarations]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|136|warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /home/yoohoo/ffmpeg_build/include/libavcodec/avcodec.h:3629) [-Wdeprecated-declarations]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|138|error: invalid conversion from ‘int’ to ‘AVDiscard’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|140|error: ‘avcodec_open’ was not declared in this scope|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|163|error: invalid conversion from ‘char*’ to ‘const uint8_t* {aka const unsigned char*}’ [-fpermissive]|
/home/yoohoo/ffmpeg_build/include/libavcodec/avcodec.h|4465|error: initializing argument 5 of ‘int av_parser_parse2(AVCodecParserContext*, AVCodecContext*, uint8_t**, int*, const uint8_t*, int, int64_t, int64_t, int64_t)’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|181|error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|182|error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|188|error: ‘av_get_pict_type_char’ was not declared in this scope|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|210|error: ‘sleep’ was not declared in this scope|
||=== Build finished: 9 errors, 2 warnings ===|
我想知道这是一个不兼容的问题，因为我将这个C程序移动到C ++，但我终于需要在C ++中使用它。如何解决这些无效的转换问题？提前谢谢！
答案 0 :(得分：1)
在代码的main（）函数中
char *arghwtf = malloc(INBUF_SIZE);
您已使用返回void *的malloc函数分配了内存，并且您将此void *分配给char *，这就是您收到错误的原因。你必须将它转换为char *。
相反，试试这个。
char *arghwtf =(char *) malloc(INBUF_SIZE);